The present invention is directed to a mobile terminal integrated with a position detection system and a method to minimize traffic on a mobile network.
Mobile terminals such as cellular phones, personal digital assistants, laptops equipped with wireless modems, and the like have exploded into the public consciousness. These devices enable individuals to remain connected to other people without being tied to a land-based phone.
Because mobile terminals are in fact, by definition, mobile, many recent patents have discussed incorporating position detection capabilities into the mobile terminals so that the user may know where they are. Alternatively, such technology may be used so that a third party knows where the mobile terminal is located. One such proposed use of a position detection system is to deter theft; items being protected may periodically report their present whereabouts through a wireless modem as determined by the position detection system.
One popular position detection system targeted for such incorporation into a mobile terminal is the Global Positioning System (GPS), which relies on a constellation of satellites to assist a GPS receiver in determining its location. Other terrestrial or satellite-based systems do exist, such as GLONASS, the Russian equivalent of GPS. Likewise, position detection systems have been proposed which would use base stations in a mobile network to provide triangulation data for mobile terminals within the mobile network.
Unfortunately, while integration of position detection systems and mobile terminals seems like a laudable goal and is technically feasible, such integration may tend to ignore the realities behind such position detection systems and mobile networks.
For example, GPS has an extremely slow data transfer rate. It may take on the order of ten to twenty minutes to secure enough information from the satellites to determine position without any a priori knowledge. While GPS may be an extreme example, other positioning systems may experience similar delays. Inability to secure quick position information may lead to consumer frustration. In a theft deterrent usage, the long lag in determining a position of a stolen item may hinder recovery efforts.
Several solutions to this problem have been proposed, although presently without any significant commercial exploitation. In a first solution, “almanac” information is stored in the mobile terminal so that the mobile terminal can determine approximately where in the sky to search for satellite signals from which to determine position. In a second solution, the mobile terminal inquires over the mobile network to a server about the precise present location (“ephemeris”) of the satellites.
While these solutions may assist the mobile terminal in determining where to look for satellites from the GPS, they still are not satisfactory. The first solution does not speed up the location determination process that much. Even where a complete set of almanac information is available in the mobile terminal, it may take on the order of a full minute to receive enough information from the GPS satellites to determine the precise location of the mobile terminal. The second solution creates a huge bandwidth demand on the mobile network since the ephemeris information is sent about all the satellites, not merely the ones visible. Such ephemeris could be broadcast to multiple mobile terminals over a shared control channel, or provided in individual responses to requests from mobile terminals. Since the common control channel is typically a scarce resource, clogging it with lots of ephemeris information may preclude another service. While providing ephemeris in individual responses to requests alleviates this problem, it is relatively inefficient from a network management point of view. Moreover, when the number of mobile terminals requesting ephemeris data increases, the problem of using bandwidth, another scarce resource, is not alleviated.
Thus, there is a need for a system or technique that limits reliance on information from the position detection system, whether that information be provided directly from the position detection assisting devices or from a server that has received that information from the position detection system.